// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// SampleVector implements HistogramSamples interface. It is used by all
// Histogram based classes to store samples.

#ifndef BASE_METRICS_SAMPLE_VECTOR_H_
#define BASE_METRICS_SAMPLE_VECTOR_H_

#include <stddef.h>
#include <stdint.h>

#include <memory>
#include <vector>

#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/metrics/histogram_base.h"
#include "base/metrics/histogram_samples.h"

namespace base {

class BucketRanges;

class BASE_EXPORT SampleVector : public HistogramSamples {
public:
    explicit SampleVector(const BucketRanges* bucket_ranges);
    SampleVector(uint64_t id, const BucketRanges* bucket_ranges);
    SampleVector(uint64_t id,
        HistogramBase::AtomicCount* counts,
        size_t counts_size,
        Metadata* meta,
        const BucketRanges* bucket_ranges);
    ~SampleVector() override;

    // HistogramSamples implementation:
    void Accumulate(HistogramBase::Sample value,
        HistogramBase::Count count) override;
    HistogramBase::Count GetCount(HistogramBase::Sample value) const override;
    HistogramBase::Count TotalCount() const override;
    std::unique_ptr<SampleCountIterator> Iterator() const override;

    // Get count of a specific bucket.
    HistogramBase::Count GetCountAtIndex(size_t bucket_index) const;

protected:
    bool AddSubtractImpl(
        SampleCountIterator* iter,
        HistogramSamples::Operator op) override; // |op| is ADD or SUBTRACT.

    virtual size_t GetBucketIndex(HistogramBase::Sample value) const;

private:
    FRIEND_TEST_ALL_PREFIXES(HistogramTest, CorruptSampleCounts);
    FRIEND_TEST_ALL_PREFIXES(SharedHistogramTest, CorruptSampleCounts);

    // In the case where this class manages the memory, here it is.
    std::vector<HistogramBase::AtomicCount> local_counts_;

    // These are raw pointers rather than objects for flexibility. The actual
    // memory is either managed by local_counts_ above or by an external object
    // and passed in directly.
    HistogramBase::AtomicCount* counts_;
    size_t counts_size_;

    // Shares the same BucketRanges with Histogram object.
    const BucketRanges* const bucket_ranges_;

    DISALLOW_COPY_AND_ASSIGN(SampleVector);
};

class BASE_EXPORT SampleVectorIterator : public SampleCountIterator {
public:
    SampleVectorIterator(const std::vector<HistogramBase::AtomicCount>* counts,
        const BucketRanges* bucket_ranges);
    SampleVectorIterator(const HistogramBase::AtomicCount* counts,
        size_t counts_size,
        const BucketRanges* bucket_ranges);
    ~SampleVectorIterator() override;

    // SampleCountIterator implementation:
    bool Done() const override;
    void Next() override;
    void Get(HistogramBase::Sample* min,
        HistogramBase::Sample* max,
        HistogramBase::Count* count) const override;

    // SampleVector uses predefined buckets, so iterator can return bucket index.
    bool GetBucketIndex(size_t* index) const override;

private:
    void SkipEmptyBuckets();

    const HistogramBase::AtomicCount* counts_;
    size_t counts_size_;
    const BucketRanges* bucket_ranges_;

    size_t index_;
};

} // namespace base

#endif // BASE_METRICS_SAMPLE_VECTOR_H_
